1. Technical Field
The present invention relates to a method for operation of a wind energy installation, with the wind energy installation having a rotor which can be driven by wind, having at least one rotor blade, a generator for conversion of the mechanical energy of the rotor to electrical energy, as well as a tower on which the rotor is arranged. The invention also relates to a wind energy installation for carrying out the method.
2. Related Art
In the case of wind energy installations in which the rotor as well as the rotor blades rotate about an at least approximately horizontal axis, with the rotor being mounted at the upper end of the tower, the rotor blades each successively pass over the area of the tower during operation. During operation, that is to say while the rotor blades are rotating, severe wind loads frequently lead to the rotor blades bending in the direction of the tower. The higher the wind speed which strikes the rotor blades and drives them, the greater is the bending which can be observed on the rotor blades. One other influencing factor for the intensity of the bending movement is, of course, the length of the individual rotor blades. The longer a rotor blade is, the more severely it will bend. Since the trend in wind energy installation design is to construct ever larger wind energy installations with ever longer rotor blades, the intensity of the bending will increase ever further.
In the extreme, the rotor blades even in wind energy installations that are used nowadays bend so severely that this can result in the rotor blade which is passing the tower area touching the tower. In this case, contact with the tower normally leads at least to serious damage to the rotor blade, and possibly also to the tower. In order to prevent such damage, it is known in the prior art on the one hand for the rotor axis to be inclined slightly upwards with respect to the horizontal, so that the distance between the rotor blade and the tower is increased while passing the tower. On the other hand, it is known for the rotor blades to be bent somewhat in the opposite direction to the tower direction after they have been manufactured, in order to counteract any subsequent wind load bending. Despite these measures, contact between the tower and the rotor blades, particularly the rotor blade tips, has still occurred in the past with the described effects.
One object of the present invention is thus to specify a method for operation of a wind energy installation which allows contact between the tower and the rotor blades to be effectively prevented. A further object of the invention is to specify a wind energy installation which operates using this method.